Pile driving method and apparatus

ABSTRACT

Driving of piles into submerged lands with a steadily applied force of sufficient magnitude to appreciably deflect the subsoil, with or without superimposed driving pulses.

United States Patent [1 1 Wisotsky I 1 1 NOV. 12, 1974 PILE DRIVINGMETHOD AND APPARATUS Inventofl $9rse-fl2t$a 9298 311 89 Bullard St.,Sharon, Mass. 02067 Filed: June 30, 1972 Appl. N0.: 267,752

Related U.S. Application Data ('unlinuutiun-in-purt ut'Scr. No. 163.422,July 16, 1971, abandoned.

References Cited UNITED STATES PATENTS 6/1896 Washington 61/5374 X2/1944 Brizay 61/53 2,536,908 1/195 1 Chadwick" 37/73 X 2.830.788 4/1958Bentley ct al..... 2 4/106 X 2,881,591 4/1959 Reeve 61/465 2,940,2666/1960 Smith 61/465 3,054,463 8/1962 Bodine 173/49 X 3,263,641 8/1966Stimson 1 14/206 3.406524 1'0/1968 Blenkarn ct a1. 61/535 3,604,5199/1971 Chelminski 173/1 3.833.118 5/1958 Nixon 61/465 FOREIGN PATENTS ORAPPLICATIONS 246,350 H1926 Great Britain 61/535 398,627 10/1921 Germany61/5 5 Primary Examiner-Jacob Shapiro Attorney, Agent, or Firm-Robert R.Priddy 37 Claims, 8 Drawing Figures BACKGROUND Mammoth structures 'of15,000 to 40,000 tons air weight are currently planned for offshoreinstallations such as ship terminals, oil drilling, production, andstorage. Although engineering problems are severe, no.

doubt, larger and heavier ones will appear in the future.

Heavy storms, large vessel-bumping, earthquakes, ice floes and the likewill readily dislodge and topple structures weighing tens'of thousandsof tons unless they have suitable foundations. Anchoring problems areparticularly acute in deep water and where the structures extend abovethe surface. Undersuch conditions, large structures, and particularlytall ones, exert tremendous pullout forces on their foundations. Failureof the anchoring system means catastrophic failure, causing death orinjury to personnel on duty on the structure, widespread exterminationof marine life by oil released when oil drilling, productiomor storagestructures are damaged, and loss of stupendous amounts of investedcapital. v

The most prevalent foundation method is to drive piles into the seabottom through or adjacent the lower portion of the structure and securethe structure to them. Usually the most severe requirement is that thepiles will not pull out during storm conditions. Consequently, they mustpenetrate deep into the seafloor, and the driving process must ofnecessity'continue well beyond the point at which the resistance todriving becomes severe.

Experience has shown that contemporary steam-' hammer and vibratorypile-driving techniques alone are unable to fully emplace those pilesof, for instance,

200 tons air weight which are used for the larger offshore structures.Thus, although'powerful steam hammers have developed, the largest ofwhich are so rela tively heavy that they become difficult to handleunder storm conditions, they are still inadequate to drive many offshorepiles efficiently.

In the inelastic collision process between a hammer and pile, theefficiency of energy transfer from the striking mass (hammer) to thedriven mass (pile) varies as the ratio of the striking mass to the totalotthese two masses. For this reason, land-based pile-driving practicerecommends for most economical results that the striking mass(approximately one-half of the typical hammers total weight) shouldequal that of the pile. This results in a driving efficiency of about50%. Specifically not advised is the use of a driving mass having a ramweight less than one-fourth of the pile. Notwithstanding, the largestcontemporary hammers used in offshore/marine work are limited,practically, by storm-weather handling requirements, to weights on I theorder of about 60 tons (striking mass 30 tons). Consequently, theyusually are inadequate to drive the larger piles due to mass-mismatch.

For instance, with a 200 ton pile, the energy transfer efficiency of a30 ton striking mass would be 100% X 30/(30+200) or only 13%. However,to make matters worse, even this relatively small amount of energytransferred to the pile is not altogether-effective in driving due tomechanical compliance in the pile and ground plus mechanical losses inthe hammer and pilecoupling themselves. Although such palliative meas- Iures as pre-drilling, jetting and grouting mayassist in pileemplacement, they have a deleterious effect on pile pull-out resistance.Thus, a need rema'in's'for major improvement in techniques for drivinglarge piles into the sea floor.

SUMMARY OF THE INVENTION In accordance with the invention a pile,suitably braced to control its-direction of penetration, is pushedor'pulled downwardly into the sea floor'with a steadily applied forcesufficiently large to appreciably deflect the sub-soil beneath the lowerend or tip of the pile. Re petitive driving pulses superimposed upon thesteadily applied force in combination, provide the force necessary todrivethe pile. A more efficient application of the availabledrivingenergy maythus be attained. This steadily applied forces of theorder of 200,000 pounds and preferably 500,000pounds or more arecontemplated. Driving piles in accordance with theinvention reduces idleenergy storage and permits deeper driving than has heretoforebeeneconomically feasible, or at least technically possible, withconventional impact hammers or vibratory methods. When the pilepenetrates the ground under the action ofsuch a driving force, a portionof the kinetic energy imparted to the pile is converted intonon-productive potential energy in the reversible elastic deformation ofthe soil and the pile. Such deformation is referred to as ground quake.The steadily-applied large forces employed in this invention maintainthe sub-soil benath the pile tip in a deformed and pre-stressedcondition, thereby reducing the unavailable energy stored in groundquake;

and, this is true whether driving is accomplished with the steady forcealone or in combination with superimposed-repetitive driving pulses.Also, when using superimposed impulses generatedby deceleration of adownward moving mass, one can apply the deflective force in such amanner as to reduce the driven mass, thereby improving the efficiencywith which. driving energy is transmitted to the pile. These and otheradvantages will become apparent from the description of certainpreferred embodiments of the invention, described below.

BRIEF DESCRIPTION OF THE DRAWlNGS In the drawings, wherein likereference numeralsfloor by a pile or suction-anchor and which extendupwardly to attach points on the pile.

FIG. 2 is a schematic diagramof a pile being driven through the foot ofan offshore oil exploration structure wherein the load is provided by acombination of a hydraulic cylinder at the top of the structure andchain threaded from the cylinder through pulleys at the foot of thestructure and extending upwardly to attach points on the pile.

FIG. 3 is a schematic diagram of a pile being driven into the sea floor,wherein the force is provided by a floating object, e.g., barge, havingpile gripping means and fluid-actuated cylinders and pistons adapted totransfer at least a portion of the barges weight from the water to thepile.

FIG. 4 is a schematic diagram of temporary anchoring means useful inanchoring pulleys, winches, barges and the like in conjunction withdriving piles in accordance with the invention.

FIGS. 5-7 are sectional views, partly broken out, of an impulsivedevice.

FIG. 8 is a schematic diagram showing the driving of a pile using aforce transmitted by cable from pulleys or remote control winchesmounted on the temporary anchoring means of FIG. 4 and in which thedriving device of FIGS. 5-7 is used to superimpose driving pulses uponthe force provided by the cables.

In the embodiment of FIG. 1, there is a pile 10 having its tip 11embedded in the sub-soil 12 of a body of water 13. Releasably positionedon the pile is clamp 14, which may be a mechanical scroll, hydraulicallypneumaticaly operated chuck controlled by cable 33 from surface powerconsole 34 and raised by its own winch 35 via line 36 from barge 31. Tothe clamp 14 are attached the upper pulleys 15 and 16 of the two sets ofblock and tackle 17 and 18 arranged to pull downwardly on the pile. Theblocks and tackle include cables l9 and 20 extending downwardly fromupper pulleys 15 and 16 to lower pulleys 21 and 22. The latter may beanchored in any desired manner such as for example to a suction anchor23 more fully disclosed in FIG. 4 or by a clamp 24 to a pile 25 whichhas previously been embedded in sub-soil 12.

Two sets of block and tackle are shown, but any desired number may beused. The block and tackle sets may be used with various auxiliaryarrangements of anchors, cables, templates, guides, and/or other meansfor bracing the pile 10 and controlling its direction of penetrationinto sub-soil 12. Such auxiliary arrangements will readily be suppliedby those skilled in the art, and are therefore not shown in the drawing.When suchauxiliaries are omitted altogether, it may be found desirableto use three, four or more sets of block and tackle. When the latterperform both pulling and bracing functions, they may, if desired, bearranged on radii of the piles longitudinal axis which are perpendicularthereto and have approximately equal angular spacing relative to oneanother; and the lower pulleys 21 and 22 will be situated at radialdistances from the pile that are appropriate both for pulling the pilevertically and holding it at the desired driving angle, as shown inFIG. 1. When one or more block and tackle sets are used solely fordownward pulling, the lower pulleys 21 and 22 may be set quite close tothe pile 10.

The number and positions of the block and tackle sets, the number ofsheaves in the blocks and the tensile rating of the cables will also beselected in reference to the force which is to be applied. The force isone which will deform the subsoil in excess of the ground quake" asdefined by R. D. Chellis, Pile Foundations, McGraw Hill, 1961, or E. A.L. Smith Pile-Driving Analysis by the Wave Equation, J. Soil Mechanicsand Foundations Div., Proc. A. S. C. E., AUG. 1960.

On a barge 31 floating upon. the surface 32 of water 13 above pile 10are winches 29 and 30. Portions 27 and 28 of cables 19 and 20extenddownwardly from the winches through the water and through the pulleymeans 21 and 22, these pulley means being situated at fixed pointsdefined by anchor 23 and pile 25. By operation of the winches, cableportions 27 and28 are drawn upwardly, drawing the upper (15, 16) andlower (21,22) pulley means together, thereby pulling the pile 10upwardly into the soil. The downwards force advantage exerted by theblock and tackle combination 15, 17, 19, 21 over the tension in line 27is, theoretically, the number of strands between the blocks 15 and 21,consequently the load-on the surface vessel 31 is reduced by thismechanical advantage ratio.

In the embodiment of FIG. 2 is illustrated the em placement of anoffshore oil drilling or production structure which is fabricatedonshore, set in place on the bottom of the sea and secured in place bydriving piles at the foot of the structure. The structure 40 includes abase 41, resting on the sub-soil 12. From base 41 extend upwardlygenerally upright supports 42 and 43 which pass upwardly through thewater 13 to a platform '44 above the surface 32. The structure is bracedby vertically-spaced horizontal members 45, 46 and 47, extending betweenthe upright members 42 and 43. Various diagonal supports 48 also serveto brace the structure.

In FIG. 2 may be seen a previously emplaced pile 25 41 into sub-soil 12.A collar 50 tightly secured around the upper end of pile 25 against theupper surface of base 41 secures the structure to the pile.

Through another aperture 51 through the other side of base 41, a pile 10is being driven. To a clamp 14 is attached a chain 52. The latterextends downwardly from clamp 14 along the side of the pile 10 to apulley 53 secured to base 41. From this pulley the chain extendsgenerally horizontally to a second pulley 54 also secured to base 41near the center of the structure. From pulley 54, the chain extendsupwardly through water 13 and through an aperture 55 in platform 44.After passing through releaseable gripping jaw 56, the chain passes to awind-up drum 57. Jaw 56 is attached to the piston rod of hydrauliccylinder 59 supported on platform 44 by legs 58 above aperture 55.Operation of the cylinder upwardly exerts an upward pull on the chain asit passes from the winch to pulley54 and a downward pull on pile 10 atcollar 14. When pile 10 has been driven into the sub-soil to the desiredpoint, it may also be secured by a collar like the collar 50 on pile 25.

It should be appreciated that in the preceding two embodiments, themeans chosen for anchoring the pulleys may be freely varied. The lowerpulleys may be secured to any fixed point or member having the requisiteholding power. Any desired combination and number of pulleys may beemployed. Also the chain or cable may be drawn upwardly by any means.However, when the cable or chain is drawn upwardly by a fluid actuatedpiston and cylinder combination mounted on a barge, platform orelsewhere, and the'piston and cylinder combination are provided withreleasable means for coupling it to the chain or cable, long lengths ofchain or cable may be pulled in increments of length corresponding tothe stroke of the piston. Also, the suction anchor 23 may be used tohold down the structure 40 by means of block and tackle 15, 17, 19, 21and a clamp 14.

FIG. 3 discloses application of the force as a downward push on thepile. The drawing shows the pile already partially emplaced with its tip11 embedded in subsoil 12. The remainder ofpile 10 extends upwardlythrough water 13, breaking through the waters surface 32 in a slot orwell 60 provided in a floating barge 61. The barge is held in placeradially and vertically relative to the pile by anchor lines 62, 63,anchors 64, 65, and other anchors and lines as required.

In order to conserve space in the drawing the water depth, anchor lines62, 63 and pile 10 are foreshortened. In order that the slot or well 60and means for pushing downwardly on the pile may be better seen, aportion of the barge around the slot or well 60 has been broken out inthe drawing. Within the broken out portion of the drawing is areleasable clamping collar 66 which may be squeezed together or releasedby operation of a fluid actuated cylinder and piston combination 67. Aplurality of pile-pushing cylinder and piston combinations 68, 69 aresecured to clamping collar 66 at spaced points-around the pile 10. Theopposite ends of cylinder 68, 69, are supported by generally uprightframeworks 70 and 71 erected upon the upper surface of the barge.

In this embodiment, the required soil-deforming force is applied byreleasing clamping collar 66, re-

. tracting cylinders 68, 69, gripping the pile with cIamping collar 66by energizing cylinder 67 and actuating cylinders 68 and 69 to extendthem. In this manner, a portion of the weight of barge 6,1 istran'sferred'to pile 10. If desired, water may be pumped into the bargeto increase the force exerted on the pile, or fixed ballast may be used.

After pile tip 11 has been pushed some distance further into sub-soil12, cylinders 68 and 69 may be retracted, gripping collar 67 beingreleased so that it can again grip the pile, this time at a positionsomewhat closer to the top of the pile. The operation may be carried outrepetitively until the pile has penetrated the sub-soil to the desiredextent.

It should be noted that if impulsive or vibratory forces aresuperimposed upon the static force by means of a hammer or vibrator, thebarge mass can be decoupled from the pile during downward motion of thelatter, if efflux from the cylinder on the low-pressure side of thepiston is not impeded.

FIG. 4 discloses one example of an anchoring means suitable for use inthe same manner as anchor 23 of FIG. 1. This suction anchor includes abase 80 having a peripheral, downwardly extending rim 81 adapted topenetrate the sub-soil 12. Within and secured to rim 81 is a gradedscreen 82 which is spaced downwardly from the underside of base 80 toprovide a suction chamber 83. A differential pressure pump 84 is alsomounted in base 80 with its suction port within chamber 83. In order toreduce the opportunities-for hydraulic shortcircuiting from the pumpoutlet around the outside of rim 81 and back into suction chamber 83, anelastomeric pressure skirt is secured around the periphery of 6 baseextending generally horizontally and outwardly from the base. in alldirections. When pump 84 is energized, a portion of the ambienthydrostatic head is employed to provide firm anchoring to the subsoil12.

An analysis of the operation of hydrostatic anchors reveals that theyare subject to two fundamental failure mechanisms. Onelimit is imposedby the soils hydraulic punch-through stress, thatis, resistance tohydraulic wash-outs or short-circuits resulting from the combination ofpressure gradient and associated percolation-' leakage flow produced bythe differential pressure pump 84. The second limitation is the tensilepull-out strength of the soil clumped around the base at some isobaricfraction of the differential pressure across the base. Both of theselimits may be extended by employing an evacuated well point, similar tothat disclosed in U.S. Pat. No. 2,895,301, Casagrande et al., July 21,

- 1959. A well point may for instance be a pipe having porous walls orhaving screened perforations throughout itslength and with gravelpacking inside. Use of a sub-surface well point decreases thedifferential pressure gradient by increasing the percolation leakagepath so as to result in anoverall increase in the'hydraulicpunch-through resistance of the coil. At the same time, a larger clumpof soil tends to break out with the anchor upon failure, thus adding theweight and shear resistance of that mass of soil to the anchors pull-outforce.

The preferred embodiment of the suction anchor used with the inventionincludes means for driving and retrieving such well points. A generallyupright guide and support member 85 is secured to the base 80. Any typeof suitable driver 86 is mounted on guide member 85 in amannerpermitting vertical sliding m'ovement'of the driver relative tothe guide member. This driver may for example be an electro-hydraulicservo vibrator or hydraulic hammer type driver. On the top of guidemember 85 is an apertured cap plate 89 in which, are

mounted upper pulleys 87 and 88. Lower pulleys 90 and 91 aremountedat'the lower end of vertical guide 85. These pulleys togetherwith wire 92 and remote controlled bi-directional winch 93 cooperate topull upwardly ordownwardly upon driver 86as required.

The well point 98 is secured to the driver 86, and passes through thebase 80 and screen 82 via a packing box 95 provided with-scraper ringsor an impermeable boot. A flexible hose 96 is interconnected between theinterior of the well point and a suction tap on pump 84 provides a meansfor generating a differential pressure between the hydrostatic head inthe sub-soil and the interior of the well point at the lower end of thewell point.

The suction anchor is connected with a vessel or other floating objectat the surface by a cable 99 connected to the upper end of the verticalguide and support member 85. In or along cable 99- run various electricpower, and control cables which disperse from junction box 100. Cable101 operates pump 84. Cable 102 operates driver 86. Cable 103 operatesthe bidirectional winch 93. Hydraulic. or pneumatic and controls may ofcourse be substituted.

In normal operation, the anchor is sent to the bottom with the wellpoint 98 retracted. When the suction anchor has reached the bottom, pump84 is energized to the driver is energized to force well point 98 intosubsoil 12 until its downward motion is arrested by collar 97.Evacuation of the well point, via flexible hose 96, combined with thedifferential pressure generated across the screen 82 extends thedifferential gradient influence of the suction anchor deep into theground as indicated by the isobaric lines 104 in FIG. 1. Thus a verylarge anchoring force is provided. It should be understood also thateach suction anchor may be provided with a pluralityof well points, thedriver being indexable to drive or withdraw the well points in sequence.

This anchor may be used for example as a fixed point for the attachmentof a lower pulley of a block and tackle set as shown in FIG. 1, thepulley being secured for instance to the base 80 of the suction anchor.The anchor may also be used for anchoring a barge, such as the barge 61of FIG. 3, or for any other desired purpose. When it is desired to moveor remove the anchor, the winch 93 is energized to provide an up-pull ondriver 86 while the latter is operated to assist in withdrawing wellpoint 94 from the subsoil. Pump 84 is deenergized. Then, the anchor maybe hauled to the surface or moved to a different location with the aidof cable 99.

The steadily applied force may constitute the sole force employed todrive a pile as illustrated .in FIGS. 1 through 3. However, the use ofasteadily applied force of the requisite magnitude substantiallyenhances the operating efficiency of pile drivers of the type'whichdepend upon repetitive decelerations of a driving mass for theiroperation. Typical of such drivers are steam operated hammers and morepreferably water-hammer drivers. In general, the latter are devices inthe form of a long tube, coupled to the pile and having means to quicklystop a flow of liquid in the tube. The input energy is in the form offluid flow in the tube. When the flow is suddenly stopped, its momentumcreates highpowered mechanical impulse and hydraulic pressure waves ofrelatively high magnitude which propagate. at speeds approaching that ofsound in the fluid. In effect, the action is that of a fluid spear orram.

Water hammer drivers can'be fabricated in a wide variety ofconfigurations, one illustrative example of which is shown in FIGS.through 7 hereon. FIG. 5 represents a configuration of a pile l0 drivenunderwater into the ground 12 by a top-mounted hammer. The pile issecurely fastened to the hammer 123 by a coupling means 122. Thiscoupling 122 may take the form of simply bolted flanges or a moresophisticated mechanical clamping arrangement similar to the scrollorpneumatically-operated machine tool lathe'chucks which are well-knownand will not be described further. The pile hammer 123 in the presentcase includes hammer tube 124, made of flanged sections of heavywalledtubing bolted together and contains a shockmounted electric motor 125hydraulic pump 126 combination near its bottom. The pump 126 evacuatesthe water out of the hammer tube 124 through a center-mounted pipe 127discharging vertically out its top. The pump I26 axially supportsthe-discharge pipe 127 or, in other configurations, vice versa. On thetopmost section of the water hammer tube 124 is mounted the fast-openingwater control valve 128, and its pneumatically operated actuator 129.When open, valve 128 freely admits water from the surrounding body ofwater through the valve body and its inlet 132 into hammer tube 124. Awire rope sling 130 supports the entire assembly from the surface andalso conveys the power and control harness 133 thereto.

The design of the water control valve 128 may be such that rapid openingthereof is aided by the force generated by the ambient hydrostatic headacting on the valve. In order to prevent the inrushing water fromexerting any drag forces on the pump 126 and motor assembly, the liquidlevel is controlled to prevent the draw-down of water to the pump level.The casings of the pump, motor and discharge pipe should be made strongenough to withstand the resulting water hammer pressure. When required,the motor-pump-discharge pipe assembly can be made free-floating andmechanically shock-isolated axially from the water hammer tube by alower compression spring (not shown) which supports the static airweight of the motor-pump-pipe assembly and an upper compression spring(not shown) which helps the gravity return of the pump assembly to itsnormal mid-position. A hydraulic type shock absorber (not shown) can beused to provide viscouc damping to reduce oscillations. Further shockresistance can be provided by making the motor-pump critical componentsneutrally buoyant in their respective liquid by means of low densityconstruction materials and high-density liquids incorporated in theirrespective frames. Motor conductors and control cables pass from thesurface to the motor 125 and valve 128 through the water-tight power andcontrol harness 133.

When the pile is of sufficient length and diameter, and also tofacilitate the handling of long assemblies, the hammer tube 124 may belocated internally within the pile as shown in FIG. 6, using anyinternal coupling, such as that (142) shown in FIG. 7. This permitsincremental upward repositioning of the hammer as the pile 10 is driveninto the bottom 12. It also permits coupling of the driver to the pileat a position which is closer to the subsoil 12 than the top of thepile, giving an improved driving action. Concentricity alignment rings152 may be secured to each water hammer tube flange joint as shown inFIG. 6.

To secure the hammer within the pile high pressure fluid is fed into thelower cylindrical cavity 153 of the pile coupler through port 154, FIG.7. This flow causes the cylinder frame 155 to move downward overthe-piston 156. The piston shaft is secured to the base 157 that isbolted to the bottom flange 148 of the water hammer tube 124. When thecylinder frame 155 moves downward it creates a toggle action in themultiplicity of links 158. The resultant mechanical advantage varies asthe cotangent of the angle between the link and the radial normal.Consequently, hard-tooth shoes 159 slide radially outward in T slotguides in the base 157 and bite into the pile walls. Simultaneously, thefluid in the upper cylindrical cavity 160 is exhausted through port 161.A 4-way electrically controlled valve (not shown) can be used to controlthe influx and efflux of the pressurized fluid, which may be hydraulicor air. To release the pile coupler, the influx and efflux ports on thepiston base are interchangeable by control valve action. The compressionspring 162 in the upper cylinder 160 retracts the entire mechanism whenthe air pressure is off. This pile coupler'also can be used in theend-drive configuration of FIG. 5.

When the wall of the pile 10 is of sufficient internal collapse pressurestrength then it itself can assume the function of the water hammer tube124 in FIG. 6. The

FIG. 6 assembly would be modified so that the pile coupler of FIG. 7,configured to include a pressure-sealed driving flange, would be locatedbetween tube 124 and control valve 128.

Any other design of water-hammer driver may be used in the presentinvention. Included are those in which evacuation of the water isaccomplished by a piston moving in the tube 124 or by condensable vaporsinjected into or generated within the tube. In such cases, a valve isnot essential to start the flow of liquid in the hammer tube.Alternatively, the water hammer driver may be of the type in which thehammer tube remains flooded throughout its operating cycle, a fastactingvalve closing periodically to momentarily stop a flow of liquid in thetube. When operating with flooded tube drivers, the fast acting valvemay be ftuned or its closure may be controlled for instance by afeed-back circuit to provide resonant operation. In either case, meanssuch as baffles or pressure release means may be provided in the tube tocontrol the intensity of the water hammer pulses and/or to providerotational movement. Thus, operation of the water-hammer may be tailoredas desired to match the characteristics of the pile, sub-soil and otherdriving conditions.

The operating cycle of the illustrated hammer includes a relativelyslow-water evacuation phase and .a'

relatively fast power stroke. Theevacuation period, depending upon thewater-tube volume and pumping rate, ends upon the actuation of a liquidlevel switch (not shown) in tube 124 which controls opening of the watercontrol valve 128. However, since the power period may be of the orderof one second or less, the electric motor 125 driving thewater-evacuating pump need not be shut down and restarted for eachhammer cycle.

Of course, the elevation of the liquid level switch should compensatefor the water level draw-down during the driving period. i

FIG. 8 illustrates the driving of a pile using a combination of asteadily applied force sufficient to appreciably deflect the subsoil andsuperimposed water hammer driving pulses. In the drawing, the pile 10 isalready partially embedded in the sub-soil 12 of a body of water 13. Thedriver 123 of FIG. 5 is secured to the top of pile 10 by coupler 122. Toa clamp 14 are, attached cables 19 and 20 extending downwardly to alower pulley 21 and suction anchor 23 on left side and to a remotecontrolled winch 180 and suction anchor 181 on the right. These suctionanchors are both provided with well points 94 as in the FIG. 4 anchorembodiment.

On a barge 31 floating upon the surface 32 of water 13 above pile 10 isa winch 29. Portion 27 of cable 19 extends downwardly from the winchthrough the water and through the pulley 21. Thatpulley andthe winch 180are situated at fixed points defined by suction anchors 23 and 181. Byoperation of the winches, cable portion 27 is drawn upwardly while cable20 and the remainder of cable 19 are drawn downwardly. Simultaneously,driving pulses are generated in the water hammer driver 123. Thus, thepile 10 is pulled and impulsively driven downwardly into the soil.

Cables 19 and 20 may, if desired, be attached to clamp 14 throughsprings 182 and 183. Normally, the winches are operated to keep thecables tight and free from slack, or at least to take up before the nextdriving pulse any slack that becomes available during downward movementsof the pile. Springs are perhaps more useful when using chains than withcables,

. 10 as wire rope cables ordinarily have enough elasticity to remaintaut if the take-up of the winch momentarily lags behind the downwardprogress of the pile.

Virtually any vibratory or impulsivedriver may be used with a steadilyapplied soil deflecting force applied with any suitable means. Forinstance the driver may be situated above or below the water surface,atop, within or alongside the pile, or with the pile itself constituting part of the driver, while applying the soildeflecting force inany of the various ways illustrated herein. However, the best mode ofpractising the invention is to apply the soil deflecting force with awire-rope block and tackle and to apply impulsive force with a waterhammer. If the water is reasonably deep, e.g., more than 200 feet deep,it is considered best to employ a submerged water hammer able to drawupon the hydrostatic head, and, insofar as possible, to couple the waterhammer to the pile at a point which is closer to the sub-soil than tothe top of the pile.

It is to be understood that the steadily applied force referred toherein is in addition to the weight of the pile itself, and is muchgreater'than the preloads which 'would be considered appropriate invibratory driving practice. Thus, when vibrations are superimposed onthe steady soil-deforming force, said steady force will be at least 200%of the peak force generated by the vibration and will deform the soil toat least about half, more preferably toabout and most preferably toabout the equivalent of full .ground quake. Full ground quake isgenerally considered to be about 0.1 inch.

Because of the steadily applied force, at least a significant portion ofthe reversible elastic deformation of the soil is eliminated as a factorin the operation of the driver. It is nolonger necessary for the driverto repetitively supply the energy required for the elastic deformationof the piles and soil which, in spite of its reversible character,cannot be utilized" and therefore is wasted. Consequently, a greaterportion of the power of the driver is therefore available for drivingthan would be available in the absence of the soil-deforming force.Moreover, when the force is applied by chain or wire rope cables,'ratherthan a static deadweight, the application of such force does not resultin a large increase in the driven mass, e.g., the weight added can beless than one-fourth of the force applied. Accordingly, as can be seenfrom a reconsideration of the prior discussion of driving efficiency,the use of chain or cables to provide the requisite force increases thedriven mass only slightly, thereby providing a much higher energytransfer efficiency than would be obtained if the force were provided bya deadweight coupled to the pile. Additional benefits may beobtainedwhen the driver isv a water hammer type, as such hammers offerthe longer driving impulse and greaterdriving power at a lower overallweight. This in turn favorably affects driving efficiency. Moreover,since the driving mass of such drivers is water which can beconveniently drained from the apparatus during handling (as opposed tothe metal hammer which cannot conveniently be removed from theconventional steam hammer every time it is lifted by a crane) waterhammers offer the possibility of both improved handling during stormconditions and higher driving power.

The driver, including a water hammer driver, may be secured to the pileabove the surface of the water when the pile is sufficiently tall and ifthe water hammer driver includes a water .reservoir which is preferablypressurized. However, significant advantages are obtained with theevacuated tube water-hammer driver if such is situated below the surfaceof the water. Then it may draw water from the surrounding body of water,thereby using to advantage the potential energy available from thehydrostatic head. The deeper the operation, the greater the amount ofpotential energy available. Furthermore when the piles design length isless than the water depth, extra, otherwise unnecessary, length need notbe provided for driving purposes.

Although the invention has been referred to as including the use of awater hammer, liquids of densities heavier and lighter than water likecarbon tetrachloride or mercury may be used in the hammer tube toachieve proportionally greater or lesser mechanical impulses.

Accordingly, it is apparent that the invention is a broad one and thatmany changes can be made without departing from the scope of theinvention.

What is claimed is:

1. In a method of driving piles into soil with a vibratory or impulsivedriving means adapted'to subject the pile to repetitive vibrations orpulses for driving same, the improvement which comprises: subjecting thepile to a steadily applied, downwardly directed force which is at least200% of the peak force generated by any such vibration, whichsubstantially exceeds the inciden tal preload provided by the drivingmeans and pile, and which is of sufficient magnitude to appreciablydeflect the subsoil in which the pile is embedded for maintaining saidsoil in a deformed and prestressed condition, and driving the pile bysuperimposing said vibrations or pulses upon said steadily appliedforce, thereby reducing the amount of available driving energy whichwould otherwise be lost in the reversible elastic deformation of thesoil and pile.

2. A method in accordance with claim 1 wherein the force is at least200,000 pounds.

3. A method in accordance with claim 1 wherein weight added by the meansapplying the force is less than one-fourth of the steadily appliedforce.

4. A claim in accordance with claim 1 wherein said deflection is atleast about 0.05 inch.

5. A method in accordance with claim 1 wherein said force is applied bypulling downwardly on a portion of the pile.

6. A method in accordance with claim 5 wherein said downward pull isapplied by means attached to at least one fixed point beneath thesurface ofa body of water.

7. A method in accordance with claim 6 wherein said fixed point is amember anchored to the bottom of said body of water by suction.

8. A method in accordance with claim 6 wherein said fixed point is apreviously emplaced pile.

9. A method in accordance with claim 6 wherein said fixed point is aportion of an off-shore structure which is to be anchored in place atleast in part by said pile.

10. A method in accordance with claim 6 wherein the means for applyingsaid force includes a chain or cable attached to said pile and extendingdownwardly through the water block and tackle pulley means to said fixedpoint and then upwardly to pulling means for exerting an upward pull onsaid chain or cable.

11. A method in accordance with claim 10 wherein said pulling means is awinch.

12. A method in accordance with claim 10 wherein said pulling means is acylinder and a fluid-actuated piston.

13. A method in accordance with claim 10 wherein said pulling means islocated above the surface of the water.

. 14. A method in accordance with claim 13 wherein said pulling means ismounted on a floating object.

15. A method in accordance with claim 13 wherein said pulling means ismounted on a portion of an offshore structure which is to be anchored inplace at least in part by said pile.

16. A method in accordance with claim 1 wherein said force is applied bymeans pushing downwardly on a portion of the pile.

17. A method in accordance with claim 16 wherein the pushing means isattached to a floating object.

18. A method in accordance with claim 17 wherein the pushing means issecured to said floating object at least partly above the surface of thewater.

19. A method in accordance with claim 16 wherein the pushing meansincludes a cylinder and fluidactuated piston interconnected with meansfor releasably gripping said pile.

20. A method in accordance with claim 1 wherein said force is applied bya plurality of pushing and/or pulling means.

21. A method in accordance with claim 20 wherein said pushing and/orpulling means-assist in bracing the pile to control its direction orpenetration into the subsoil.

22. A method in accordance with claim 21 wherein said pushing and/orpulling means are the sole means for bracing the pile during at least aportion of the driving of said pile.

23. A method in accordance with claim 21 wherein the pile is braced andits direction of penetration into the sub-soil is controlled at least inpart by apportioning the force among said pushing and/or pulling means.

24. A method in accordance withclaim 1 wherein said force is at least500,000 pounds.

25. A method in accordance with claim 1 wherein said force is sufficientto produce a deflection of about 0.1 inch in the subsoil.

26. A method in accordance with claim 1 wherein said driving means is animpulsive driving means and said pulses are liquid hammer drivingpulses.

27. A method in accordance with claim 1 wherein said force is applied bypulling downwardly on a portion of the pile.

28. A method in accordance with claim 27 wherein the means for applyingsaid force includes at least one chain or cable interconnected with saidpile and extending downwardly, said chain or cable being pulleddownwardly.

29. A method in accordance with claim 27 wherein the means for applyingsaid force includes a chain or cable attached to said pile and extendingdownwardly through the water by block and tackle pulley means to saidfixed point and then upwardly to pulling means for exerting an upwardpull on said chain or cable.

30. Apparatus including a pile which is embedded in but not yet fullyemplaced in the subsoil of a body of water, force applying meansincluding at least one chain or cable connected to said pile above thesubsoil and extending downwardly from the point of attachment forsubjecting the pile to a steadily applied downwardly directed force ofat least 200,000 pounds, exclusive of the weight of the pile itself, theweight of said force applying means being less than one-fourth themagnitude of said force.

31. Apparatus in accordance with claim 30 wherein said pile is coupledto an impulsive or vibratory pile driving means, said force-applyingmeans including a floating object and a means for transferring at leasta portion of the weight of said object from the water to said pile andmeans for decoupling the mass of said object from said impulsive orvibratory pile driving means.

32. A method in accordance with claim 26 wherein said liquid hammerdriving pulses are generated with water from a body of water in whichthe pile is at least partly submerged.

33. In a method of driving piles into soil with vibratory or impulsivedriving means adapted to subject the pile to repetitive vibrations orpulses for driving same, the improvement which comprises subjecting thepile to a steadily applied, downwardly directed force which is at least200% of the peak force generated by any such vibration, whichsubstantially exceeds the incidental preload provided by the drivingmeans and pile, and which is of sufficient magnitude to deflect thesubsoil in which the pile is embedded to at least about half theequivalent of full ground quake for deforming and prestressing saidsoil, and driving the pile by superimposing said vibrations or pulsesupon said steadily applied force, thereby reducing the amount of drivingenergy which would otherwise be lost in the reversible elasticdeformation of the soil and pile.

34. In a method of driving piles into soil with vibra' tory or impulsivedriving means adapted to subject the pile to repetitive vibrations orpulses for driving the same, the improvement which comprises; pullingdownwardly on a portion of said pile to apply thereto a steadilyapplied, downwardly directed force which is at least 200% of the peakforce generated by any such vibration, which substantially exceeds theincidental preload provided by the driving means and pile, and which isof sufficient magnitude to appreciably deflect the subsoil in which thepile is embedded for maintaining said soil in a deformed and prestressedcondition,

and driving the pile by superimposing said vibrations or pulses uponsaid steadily applied force, thereby reducing the amount of drivingenergy which would otherwise be lost in the reversible elasticdeformation of the soil and pile.

35. A method in accordance with claim 34 wherein the means for applyingsaid force includes at least one chain or cable interconnected with saidpile and extending downwardly, said chain or cable being pulleddownwardly.

36. ln a method of driving piles into the floor of a body of water withan impulsive driving means adapted to subject the pile to repetitivepulses for driving same, the improvement which comprises: subjecting thepile to a steadily applied downwardly directed force which substantiallyexceeds the incidental preload provided by the driving means and pile,which is of sufficient magnitude to appreciably deflect the subsoil inwhich the pile is embedded for maintaining said soil in a deformed andprestressed condition, and'which is applied by means having a weight ofless than one-fourth the force applied, and driving the pile bysuperimposing liquid hammer-driving pulses upon said steadily appliedforce, thereby reducing the amount of driving energy which wouldotherwise be lost in the reversible elastic deformation of the soil andpile.

37. In a method of driving piles into the floor of a body of water withimpulsive driving means adapted to subject the pile to repetitive pulsesfor driving same, the improvement which comprises: pulling downwardly ona portion of the pile with chain or cable for applying a downwardlydirected force which substantially exceeds the incidental preloadprovided by the driving I means and pile, and which is of sufficientmagnitude to deflect the subsoil in which the pile is embedded to at.least about half the equivalent of full ground quake for deforming andprestressing said soil, and driving the pile by superimposing waterhammer driving pulses upon the force applied by said chain or cable,said water hammer pulses being generated with water from said body ofwater, and thereby reducing the amount of driving energy which wouldotherwise be lost in the reversible elastic deformation of the soil andpile.

1. In a method of driving piles into soil with a vibratory or impulsivedriving means adapted to subject the pile to repetitive vibrations orpulses for driving same, the improvement which comprises: subjecting thepile to a steadily applied, downwardly directed force which is at least200% of the peak force generated by any such vibration, whichsubstantially exceeds the incidental preload provided by the drivingmeans and pile, and which is of sufficient magnitude to appreciablydeflect the subsoil in which the pile is embedded for maintaining saidsoil in a deformed and prestressed condition, and driving the pile bysuperimposing said vibrations or pulses upon said steadily appliedforce, thereby reducing the amount of available driving energy whichwould otherwise be lost in the reversible elastic deformation of thesoil and pile.
 2. A method in accordance with claim 1 wherein the forceis at least 200,000 pounds.
 3. A method in accordance with claim 1wherein weight added by the means applying the force is less thanone-fourth of the steadily applied force.
 4. A claim in accordance withclaim 1 wherein said deflection is at least about 0.05 inch.
 5. A methodin accordance with claim 1 wherein said force is applied by pullingdownwardly on a portion of the pile.
 6. A method in accordance withclaim 5 wherein said downward pull is applied by means attached to atleast one fixed point beneath the surface of a body of water.
 7. Amethod in accordance with claim 6 wherein said fixed point is a memberanchored to the bottom of said body of water by suction.
 8. A method inaccordance with claim 6 wherein said fixed point is a previouslyemplaced pile.
 9. A method in accordance with claim 6 wherein said fixedpoint is a portion of an off-shore structure which is to be anchored inplace at least in part by said pile.
 10. A method in accordance withclaim 6 wherein the means for applying said force includes a chain orcable attached to said pile and extending downwardly through the waterblock and tackle pulley means to said fixed point and then upwardly topulling means for exerting an upward pull on said chain or cable.
 11. Amethod in accordance with claim 10 wherein said pulling means is awinch.
 12. A method in accordance with claim 10 wherein said pullingmeans is a cylinder and a fluid-actuated piston.
 13. A method inaccordance with claim 10 wherein said pulling means is located above thesurface of the water.
 14. A method in accordance with claim 13 whereinsaid pulling means is mounted on a floating object.
 15. A method inaccordance with claim 13 wherein said pulling means is mounted on aportion of an off-shore structure which is to be anchored in place atleast in part by said pile.
 16. A method in accordance with claim 1wherein said force is applied by means pushing downwardly on a portionof the pile.
 17. A method in accordance with claim 16 wherein thepushing means is attached to a floating object.
 18. A method inaccordance with claim 17 wherein the pushing means is secured to saidfloating object at leasT partly above the surface of the water.
 19. Amethod in accordance with claim 16 wherein the pushing means includes acylinder and fluid-actuated piston interconnected with means forreleasably gripping said pile.
 20. A method in accordance with claim 1wherein said force is applied by a plurality of pushing and/or pullingmeans.
 21. A method in accordance with claim 20 wherein said pushingand/or pulling means assist in bracing the pile to control its directionor penetration into the sub-soil.
 22. A method in accordance with claim21 wherein said pushing and/or pulling means are the sole means forbracing the pile during at least a portion of the driving of said pile.23. A method in accordance with claim 21 wherein the pile is braced andits direction of penetration into the sub-soil is controlled at least inpart by apportioning the force among said pushing and/or pulling means.24. A method in accordance with claim 1 wherein said force is at least500,000 pounds.
 25. A method in accordance with claim 1 wherein saidforce is sufficient to produce a deflection of about 0.1 inch in thesubsoil.
 26. A method in accordance with claim 1 wherein said drivingmeans is an impulsive driving means and said pulses are liquid hammerdriving pulses.
 27. A method in accordance with claim 1 wherein saidforce is applied by pulling downwardly on a portion of the pile.
 28. Amethod in accordance with claim 27 wherein the means for applying saidforce includes at least one chain or cable interconnected with said pileand extending downwardly, said chain or cable being pulled downwardly.29. A method in accordance with claim 27 wherein the means for applyingsaid force includes a chain or cable attached to said pile and extendingdownwardly through the water by block and tackle pulley means to saidfixed point and then upwardly to pulling means for exerting an upwardpull on said chain or cable.
 30. Apparatus including a pile which isembedded in but not yet fully emplaced in the subsoil of a body ofwater, force applying means including at least one chain or cableconnected to said pile above the subsoil and extending downwardly fromthe point of attachment for subjecting the pile to a steadily applieddownwardly directed force of at least 200,000 pounds, exclusive of theweight of the pile itself, the weight of said force applying means beingless than one-fourth the magnitude of said force.
 31. Apparatus inaccordance with claim 30 wherein said pile is coupled to an impulsive orvibratory pile driving means, said force-applying means including afloating object and a means for transferring at least a portion of theweight of said object from the water to said pile and means fordecoupling the mass of said object from said impulsive or vibratory piledriving means.
 32. A method in accordance with claim 26 wherein saidliquid hammer driving pulses are generated with water from a body ofwater in which the pile is at least partly submerged.
 33. In a method ofdriving piles into soil with vibratory or impulsive driving meansadapted to subject the pile to repetitive vibrations or pulses fordriving same, the improvement which comprises subjecting the pile to asteadily applied, downwardly directed force which is at least 200% ofthe peak force generated by any such vibration, which substantiallyexceeds the incidental preload provided by the driving means and pile,and which is of sufficient magnitude to deflect the subsoil in which thepile is embedded to at least about half the equivalent of full groundquake for deforming and prestressing said soil, and driving the pile bysuperimposing said vibrations or pulses upon said steadily appliedforce, thereby reducing the amount of driving energy which wouldotherwise be lost in the reversible elastic deformation of the soil andpile.
 34. In a method of driving piles into soil with vibratory orimpulsive driving means adapted to subject the pile to rePetitivevibrations or pulses for driving the same, the improvement whichcomprises; pulling downwardly on a portion of said pile to apply theretoa steadily applied, downwardly directed force which is at least 200% ofthe peak force generated by any such vibration, which substantiallyexceeds the incidental preload provided by the driving means and pile,and which is of sufficient magnitude to appreciably deflect the subsoilin which the pile is embedded for maintaining said soil in a deformedand prestressed condition, and driving the pile by superimposing saidvibrations or pulses upon said steadily applied force, thereby reducingthe amount of driving energy which would otherwise be lost in thereversible elastic deformation of the soil and pile.
 35. A method inaccordance with claim 34 wherein the means for applying said forceincludes at least one chain or cable interconnected with said pile andextending downwardly, said chain or cable being pulled downwardly. 36.In a method of driving piles into the floor of a body of water with animpulsive driving means adapted to subject the pile to repetitive pulsesfor driving same, the improvement which comprises: subjecting the pileto a steadily applied downwardly directed force which substantiallyexceeds the incidental preload provided by the driving means and pile,which is of sufficient magnitude to appreciably deflect the subsoil inwhich the pile is embedded for maintaining said soil in a deformed andprestressed condition, and which is applied by means having a weight ofless than one-fourth the force applied, and driving the pile bysuperimposing liquid hammer-driving pulses upon said steadily appliedforce, thereby reducing the amount of driving energy which wouldotherwise be lost in the reversible elastic deformation of the soil andpile.
 37. In a method of driving piles into the floor of a body of waterwith impulsive driving means adapted to subject the pile to repetitivepulses for driving same, the improvement which comprises: pullingdownwardly on a portion of the pile with chain or cable for applying adownwardly directed force which substantially exceeds the incidentalpreload provided by the driving means and pile, and which is ofsufficient magnitude to deflect the subsoil in which the pile isembedded to at least about half the equivalent of full ground quake fordeforming and prestressing said soil, and driving the pile bysuperimposing water hammer driving pulses upon the force applied by saidchain or cable, said water hammer pulses being generated with water fromsaid body of water, and thereby reducing the amount of driving energywhich would otherwise be lost in the reversible elastic deformation ofthe soil and pile.